and $|a| + |b| = 1$ in all cases. For example, the inverse of $(2,3,3)$ is the circulant $(1/8) (-5,3,3)$. These forms for the inverse of a positive circulant hold even when $n$ is not an ordinal. For the more general case of a positive circulant of the form $(n,n+d,n+d)$, the sum $|a| + |b| = 1/d$.